The present invention relates to an isolated probiotics preparation containing Bacillus sp. strain and a use thereof.
Currently, aquaculture is done by mass rearing and high density breeding. Since farm-raised fish is exposed to a lot of stresses and pathogenic bacteria, various antibiotic products are administered in combination with feed, thus inducing the prevention of diseases and the improvement of the growth rate. However, the use of antibiotics in animals and fish for the prevention of diseases is recently restricted for the protection of environment, and also the legal restriction for the use of antibiotics is partially enforced. Thus, an attempt to use naturally derived probiotics instead of antibiotics is appeared, and practically, it has been reported that the effect was remarkable when Lactobacillus was administrated to animals and fish as probiotics (Simirnov, V. V. et al., Microbiol. Z. 55(4): 92, 1993).
Probiotics, live bacterial preparations, prevent the settlement of harmful bacteria since the live bacteria, which are administrated to the human and animal, are concentrated and settled down on the wall of the digestive tract in intestine. Also, probiotics play a role in preventing the growth of harmful bacteria by lowering the pH inside the intestine through production of lactic acids. Furthermore, the administrated live bacterial preparation produces bacteriocin or peroxides to suppress the proliferation of pathogens, and promotes the activity of intestinal villi which serves to absorb nutrients. In addition, the live bacterial preparation produces a substance which is helpful for the absorption and utilization of nutrients, improves feed conversion ratio, and produces a substance which neutralizes a toxin caused by the pathogens. The live bacterial preparation is mostly used to suppress the reduction of helpful bacteria in the digestive tract of animals or fish caused by stress, and prevents the settlement of pathogens by adhering to a wall of bacteria-free digestive tract before the pathogens adhere to the wall, after oral administration of antibiotic products.
However, since Lactobacillus has certain specificity with an enterocyte of an animal subjected to be used, due to its species-specificity, effects of preventing and treating diseases can be achieved only if Lactobacillus should not be excreted with feces as it proliferates but adsorbed in the intestine (Conway, P. L. et al., J. Dairy Sci., 70:1, 1987). Nevertheless, most Lactobacillus sp, which are currently used as probiotics, are easily separated in the intestine of human and land animals, and are applied, as probiotics, to fish living and growing in the sea and fresh water as well, the human and land animals.
Moreover, the development of live bacterial preparations for livestock has been substantially studied in worldwide, and thereby a large number of products have been commercialized. However, live bacterial preparations for fish are few, and therefore, most recently used probiotics products exclusively used for fish in South Korea are strains imported from foreign countries, which are not adapted well to the domestic growth environment of fish. Also, since an origin of a microorganism used as probiotics for a marine fish is not a strain isolated from fish, but a strain isolated mostly from mammals, the probiotics are co-used for mammals, thus raising doubts about the effect when being applied to fish. In addition, the colony forming unit is low owing to the lack of stability caused by the time lag between import and domestic distribution because raw materials are imported. This is considered a significant problem.
Looking into related arts with regard to probiotics for fish in South Korea, Korean Patent Registration No. 206454 discloses a Lactobacillus sp. DS-12 strain isolated from an intestine of fish and probiotics using same, and Korean Patent Application Publication No. 2008-0104846 discloses a Lactobacillus pentosus PL-11 strain derived from Anguilla japonica, and probiotics for only Anguilla japonica using the same. However, the former does not have an antibacterial activity against the Streptococcus sp., which is causative bacteria of streptococcosis in Paralichthys olivaceus and Seriola quinqueradiata; and the later exhibits an antibacterial activity only in the case where a culture supernatant is treated with high concentration and also has a drawback of low availability in that it is used only for Anguilla japonica. 
Thus, the specialized live bacterial preparations for fish, which overcome the problems above, is urgently needed domestically and globally.